Large-displacement Lightweight Armor

Large-displacement Lightweight Armor Randomly entangled fibers forming loosely bound nonwoven structures are evaluated for use in lightweight armor applications. These materials sacrifice volumetric efficiency in order to realize a reduction in mass versus traditional armor materials, while maintaining equivalent ballistic performance. The primary material characterized, polyester fiberfill, is shown to have improved ballistic performance over control samples of monolithic polyester as well as 1095 steel sheets. The response of fiberfill is investigated at a variety of strain rates, from quasistatic to ballistic, under compression, tension, and shear deformation to elucidate mechanisms at work during ballistic defeat. Fiberfill's primary mechanisms during loading are fiber reorientation, fiber unfurling, and frictional sliding. Frictional sliding, coupled with high macroscopic strain to failure, is thought to be the source of the high specific ballistic performance in fiberfill materials. The proposed armor is tested for penetration resistance against spherical and cylindrical 7.62 mm projectiles fired from a gas gun. A constitutive model incorporating the relevant deformation mechanisms of texture evolution and progressive damage is developed and implemented in Abaqus explicit in order to expedite further research on ballistic nonwoven fabrics. v Acknowledgments I would like to first thank my advisor, Professor Mackin, for the good talks about engineering, science, and philosophy. Without your input and direction none of this thesis would have ever come together. I also want to acknowledge Professor Mase for his input and guidance on the modeling and continuum mechanics sections. I want to thank Jake Hundley for taking time out of his busy schedule to teach me the ins and outs of user subroutines and damage mechanics, and for the many discussions on mechanics. I want to acknowledge Thijs van Loon and all of the hard work and enthusiasm that he put in to running experiments, not to mention all of the excellent Matlab scripts he contributed, all of the Subway sandwich breaks he forced me to take, and all of the great insights he had on the project. Frank Zok for the tremendous amount of help and guidance in completing ballistic experiments on their light gas gun. I want to thank the entire grad-lab crew. Your late night/early morning antics, and dedication to working hard, but still having fun went a tremendous way in keeping my spirits up throughout the course of this thesis. Thanks to everyone that helped in some way to get all of the equipment, software, and test …